Subaru 2004 FORESTER Service Manual page 8

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3) Oil fouled:

Wet black deposits show excessive oil entrance

into combustion chamber through worn rings and

pistons or excessive clearance between valve

guides and stems. If the same condition remains

after repair, use a hotter plug.

4) Overheating:

White or light gray insulator with black or gray

brown spots and bluish burnt electrodes indicates

engine overheating. Moreover, the appearance re-

sults from incorrect ignition timing, loose spark

plugs, wrong selection of fuel, hotter range plug,

etc. It is advisable to replace with plugs having

colder heat range.

D: CLEANING

Clean the spark plugs in a sand blast type cleaner.

Avoid excessive blasting. Clean and remove the

carbon or oxide deposits, but do not wear away ce-

ramic insulator.

If deposits are too stubborn, replace the spark

plugs.

Spark Plug

E: ADJUSTMENT

Correct it if the spark plug gap is measured with a

gap gauge, and it is necessary.

Spark plug gap: L

1.0 — 1.1 mm (0.039 — 0.043 in)

IG-00026

NOTE:

Replace with a new spark plug if this area (A) is

worn to "ball" shape.

IG-00027

IG(H4SO)-7

IGNITION

(A)

IG-00028

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